Transcript File - Siegel Science

Protists
Bacteria
Viruses
Protists
 First Single-Celled Eukaryotes
 Protists means “first”
 Protists are eukaryotes that are NOT
members of the plant, animal, or fungi
kingdoms.
 Why?
Uni or Multi? That is the
question…..
 Most protists are unicellular.
 Some are multicellular.
 The largest protist is KELP - a brown algae.
An Evolutionary Tale
 Genetic & fossil evidence indicates that
eukaryotes evolved from prokaryotes and are
more closely related to present-day Archaea
than Bacteria.
 It is from multi-cellular protist that plants,
animals & fungi are thought to arose.
Endosymbosis
 Proposed by Lynn Margulis in 1966
 Ancestors of eukaryotes lived in
association with prokaryotes.
 Prokaryotes entered a host cell as
undigested food.
 They eventually began to supply
energy to the cell and became an
organelle called the mitochondria.
Grouping of Protists
 Protists are often grouped by their
mode of nutrition (a.k.a what they
eat).
 Protozoans - animal-like protists that
are heterotrophs
 Plant-like protists - autotrophs,
include algae
 Fungus-like protists - decomposers
Animal - like Protists
Plant-like Protists
Volvox
Diatoms
Spirogyra
Fungus-like Protists
How do Protists move?
 Amoeboid Movement - moving by
changing shape: process uses
pseudopods
 Cilia & Flagella - structures supported by
microtubules that protrube from the cell
surface
 Passive Movement - non-motile, depend
on other means of transportation (I.e.
water , water currents)
Pseudopod
 Greek word for “false foot”
 The cytoplasm of the amoeba streams
into the pseudopod and the rest of the cell
follows.
 Amoebas also use pseudopods to
surround and ingest prey.
Cilia & Flagella
 Cilia: Short & numerous and they move
like oars of a rowboat; protists that move
using cilia are known as ciliates.
 Flagella: relatively long, usually only one
or two per cell & they move like a wave
from basic to tip; protists that move using
flagella are called flagellates.
 Euglena can use chloroplasts to
undergo photosynthesis if light is
available or live as a heterotroph by
absorbing nutrients from the
environment.
Passive Movement
 These protists form spores
that can enter the cells of
other organisms and live
as parasites.
 Most protists inhabit the body fluids, tissues, or
cells of their hosts.
 Some parasitic protists are important pathogens
of animals, including those that cause
potentially fatal diseases in humans.
 For example, Typanosoma causes African
sleeping sickness.
 Malaria is also cause by a parasitic protist.
 Protists are found almost anywhere there is
water.
 This includes oceans, ponds, and lakes but also
damp soil, leaf litter and other moist terrestrial
habitats.
 In aquatic habitats, protists may be bottomdwellers attached to rocks or creeping through
sand and silt.
 Phytoplankton (including algae and prokaryotic
bacteria) are the bases of most marine and
freshwater food chains.
Bacteria
 Bacteria are prokaryotic unicellular
organisms.
 What does prokaryotic mean?
 No nucleus!
 What kingdom are bacteria in?
 Monera
 What Domain are bacteria in?
 Archaea and Eubacteria
Archaea
• Single-celled prokaryotes - NOT
BACTERIA but sort of like a cousin
• Tough outer cell walls that have different
amino acids which means that antibiotics
may have no effect on these
• Most live in extreme environments
(extremophiles)
1.Such as undersea hydrothermal vents
2.Great Salt Lake
Did you know….
 That your intestinal gas (a.k.a farts) are
caused by archaea - now there is
something to share with your parents at
the dinner table tonight!
Eubacteria
 Domain of Germs
 This domain is responsible for the five second
rule and why you don’t eat potato salad left in
the sun all day.
 Have been known and studies for over 150
years
 All known bacterial pathogens are Eubacteria
Discover of Bacteria
 Bacteria were unknown to people
until the 1600s,
when Anton van
Leeuwenhoek first
observed them in his
newly made microscope
So how do Bacteria fit into our
timeline of life?
 They have the
distinction of
being the oldest
known fossils, more
than 3.5 billion years
old, in fact!
 As photosynthesis in cyanobacteria
depleted CO2 in the water, layers of
calcium carbonate formed
STROMATOLITES seen above.
Probably most important..
 They shaped the course of evolution and
ecological change throughout earth's
history because they are aquatic (that is
they live in water) and are
photosynthetic (they can manufacture
their own food and produce what along
the way?)
 The genetic material of bacteria is
one double-stranded, circular DNA
molecule (not surrounded by a
nuclear membrane).
Classification
 Rod shape is called
Bacillus.
 Spiral shape is called
Spirillium.
 Spherical is called Coccus.
Classify this….
Other important contributions…
 Many ancient oil deposits are
attributed to the activity of
cyanobacteria.
 They are also important providers of
nitrogen fertilizer in the cultivation of
rice and beans.
Other fun bacteria information
 Where are Bacteria Found?
 Bacteria are found almost everywhere on
Earth:
 including in the seas and lakes
 on all continents (including Antarctica),
 in the soil,
 and in tissues of plants and animals
Food!!!!
 Bacteria have a wide range of diets.
 Some are heterotrophs.
 What are heterotrophs?
 They eat other organisms.
 Others are autotrophs.
 What are autotrophs?
 They make their own food.
Why do you care?
Negative effects:
 a. illnesses (including dental caries, strep
throat, cholera, and tuberculosis)
Positive effects:
 a. release nitrogen to plants
 b. decompose organic material
 c. fermentation (used in manufacture of cheese
and yogurt.)
Viruses: Are They Alive?
§ Life-like in that they have genes and
a highly organized structure
§ However, they are not made of cells
nor are they able to reproduce on
their own (parasite).
§ Essentially they are “genes in a
box” with a protein coat.
Examples
Damage by a Virus
 Depends how quickly the immune system
responds to fight the infection
 Ability of the infected tissue to repair itself
 For example, recovery from a cold is
common b/c our respiratory tissue
replaces damaged cells by cell division
(mitosis).
Damage - continued
 However, nerve cells don’t divide so
damage done by polio is permanent.
 So prevention of virus diseases like polio
is accomplished with vaccines.
 First vaccine was developed by Edward
Jenner for smallpox in the late 1700’s.
Vaccines
 are harmless variations of the
virus
stimulate the immune system to
mount defenses before you get
infected
Smallpox
 Contagious
 No specific
treatment
 Variola major
& minor
 Last case in the US - 1949; last case in
the world - 1977 (Somalia)
Emerging Viruses
 Viruses that have suddenly appeared
or have recently come to the attention
of scientists.
 E.g. HIV/AIDS, Ebola, Avian flu, West
Nile Virus, SARS - just to name a few
Where do they come from?
 Mutations
 Contact between
species which gives
way to species jumping
through contact and
mutations
 Spread from isolated species
Pandemics
 World-wide outbreaks of a disease
 Spanish flu (18-month period - 1918
to 1919) killed 20 MILLION ppl worldwide - that is about the same number
as the number of ppl who have died in
25 years of fighting AIDS.
Bacteriophages
 Called phages for short - what do you
think they infect?
 Their reproductive cycle
is called THE LYTIC
CYCLE.
An analogy of The Lytic Cycle
Alternative to Lytic Cycle
 Lysogenic Cycle Viral DNA
reproduces w/o
phage production
or death of the
cell.